PROJECT SUMMARY/ABSTRACT Alcohol use disorder (AUD) is a major health problem, affecting approximately four percent of people worldwide. In humans, behavioral sensitivity to consumed alcohol inversely correlates with the risk of developing alcohol dependence. Thus, mechanisms mediating alcohol sensitivity may also influence alcohol dependence, mechanisms I will investigate by primarily studying alcohol sedation in the fruit fly Drosophila melanogaster. Numerous fly genes that influence alcohol sedation have been identified and many of these genes have human counterparts (i.e. orthologous genes) that have been implicated in human alcohol abuse. The nervous system is thought to be the major site of action for the acute behavioral effects of alcohol. The nervous system in flies, like in mammals, is composed of both neurons and glia. Drosophila CNS glia are functionally and molecularly similar to mammalian glial cells. A majority of the fly genes described to date function (or are predicted to function) in neurons, leaving a major gap in knowledge about the role of glia in alcohol-related behaviors. My overarching goal is to investigate how adult-specific glial molecular mechanisms influence alcohol sedation. I will investigate whether adult CNS glia, particularly astrocytes, are synthesizing and releasing tyramine via vesicular exocytosis in Drosophila, and mammalian cell culture, to regulate alcohol sedation. The data generated from my proposed studies will be the first step toward understanding the role of glia in acute alcohol-related behaviors in animals. My studies will investigate the novel contribution of gliotransmitter synthesis and release in alcohol sedation in flies. Additionally, my studies will explore whether mammalian glial cells, like their Drosophila counterparts, are also capable of synthesizing and releasing these transmitters. The results of my studies will considerably add to our understanding of glia generally and their role in alcohol behavior specifically. My studies therefore have the potential to provide the foundation for a broader interrogation of glial mechanisms in alcohol behavior which could ultimately lead to better risk determination and treatment of AUD.